/**
 * 防抖
 * @param {function} func 相关执行函数
 * @param {number} wait 延迟时间，也就是阈值，单位是毫秒
 * @param {function} immediate func
 * @returns {function} func
 */
export function debounce(func, wait, immediate) {
  let timeout, args, context, timestamp, result

  const later = function () {
    // 据上一次触发时间间隔
    const last = +new Date() - timestamp

    // 上次被包装函数被调用时间间隔 last 小于设定时间间隔 wait
    if (last < wait && last > 0) {
      timeout = setTimeout(later, wait - last)
    } else {
      timeout = null
      // 如果设定为immediate===true，因为开始边界已经调用过了此处无需调用
      if (!immediate) {
        result = func.apply(context, args)
        if (!timeout) context = args = null
      }
    }
  }

  return function (...args) {
    context = this
    timestamp = +new Date()
    const callNow = immediate && !timeout
    // 如果延时不存在，重新设定延时
    if (!timeout) timeout = setTimeout(later, wait)
    if (callNow) {
      result = func.apply(context, args)
      context = args = null
    }

    return result
  }
}

export function isElementInViewport(el) {
  // let box = el.getBoundingClientRect()
  // return ((window.innerHeight || document.documentElement.clientHeight) - box.bottom) >= 175
  var rect = el.getBoundingClientRect()
  console.log('react', rect)

  return (
    rect.top >= 0 &&
    rect.left >= 0 &&
    rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && rect.right <= (window.innerWidth || document.documentElement.clientWidth)
  )
}
